Alfred wohl



V in two phases-that is to say, first ata tem- UNITED .MSTATES ATENTOFFICE.

Ch sinau]; wonih o'r.oHARLo TENBURe, GERMANY.

9 PROCESS OF-RECOVERI NG PROTOXID-OF-LEAD FROM WASTE PRODUCTS.

. I SPECIFICATION forming part of Letters'Patent'No. 601,299, datedMarch 29, 1898.

Application filed febrnary 1,1897. Serial No. 621,557.. (N0; specimens.)Patented in Germany May 29, 1895, No. 90,307; in France September3,1895, No. 250,022,- in Belgium November 16, 1895, No. 118,387; inEngland November 29, 1895, No.

22,359, and in Austria n ve lb r e, 1896, No. 4,577.

Tau/ll whom it may concern:

of philosophy, a subject of thelKing of Prussia, Emperor of Germany,residing at Char,- lottenburg, near Berlin, in theKingdom of Prussia,German Empire, have in vented a new and 'usefullmproved Process ofRecovering Protoxid of Load from Waste Products, (for which I'have'obtained a patent in Germany, No. 90,307, bearingdate May 29, 1895; inFrance, No. 250,022,.bearing date September 3, 1895;. in Belgium, No.118,387, bearing date, November 16, 1895; in Great Britain, No. r

22,859, bearing dateNovenlber 29, 1895, and

in Austria,"No. 4L,577, bearing date November 14, 1896;) and .Ido herebydeclare that the following is'a full, clear-,and exact descrip-; tion ofthe invention, which will enable others a skilled in the art .to whichit appertains to make and use the same.

The present invention relates to the recovering of lead protoxid fromWaste products containing lead carbonate and organic lead salts,especially from the resid-ueobtained in. the carbonation of leadsaccharate obtained by treating molasses and other impure sugarsolutions with lead protoxid; and it consists incarrying out the burningof said material perature below the melting-point of lead and then at .ahigher temperature, as hereinafter fully stated, whereby I am enabled torecover ,all the lead from said material in the form of 1895,Serial No.572,894, I have described a process forextracting the sugar. containedinv molasses and otherlike impure sugar solu-' tionsby the agency oflead protoxid; According to this process the concentrated molasses,

&0. is mixed with an excessof lead protoxid,

preferably with yellow lead protoxid, which is by far more activefor thepurpose in view than the red protoxid. The mixture is allowed to standuntil a viscous mass has formed, which is then washed with water. Thewashed mass consists of saccharate of lead and organic lead salts, thequantity of the latter of which depends uponthe greater or lesser al- Beit known thatLALFRED WOHL, doctorv 7 0 centigrade, care being taken thatthe contact between the. carbonic acid and the mass is as intimate aspossible. The introduction of carbonic acid is discontinued as soon asthe polarization of the liquor ceases to augment.

Under these conditions the residue of the carbonation step consists,essentially, of an intimate mixture of basic lead carbonate with theorganic lead salts present in the mass,

, It is obvious that the process of extracting sugar from molasses andthe like depends materiallyupon the .recovering of lead without lossesand in a form suitable for immediate reuse'that is to say, in the formof yellow protoxid. This I obtain by my process.

It is well known that lead protoxid, as well as minium, can be obtainedfrom carbonate of lead by burning the latter in the presence of air; butit has not heretofore been known that organic lead salts can be reducedto pure lead protoxid by burning. In all of the books of chemicalanalysis it is said thatby burning organic lead salts a mixture of leadprotoxid and metallic lead is obtained which has to be separated intoits constituents to enable the quantity of lead present in the salt tobe determined. The same. occurs when the residue referred to is burnedin the same way as the burning of lead carbonate is carried out.- Itresults in a greenish-colored mixture of lead protoxid with metalliclead, and it is impossible to convert this mixture into pure yellowprotoxid. Now I have dis-. covered that this failure can be efficientlyavoided by carrying out the burning in two phases under conditions aswill now be described.

The precipitate is heated for a somewhat lengthy period of time whilebeing subjected to the action of a current of air. The temperature isslowly and gently raised, however, so as to be maintained below themelting-point of lead. The mass will first assume a black color, owingto the formation of suboxid of lead (Pb O) and some metallic lead in afinely-divided state, both of which being then gradually converted intoprotoxid of lead. \Vhen the black coloring has disappeared, thetemperature is at once raised up to about (500 centigrade, whereby theyellow modification of lead protoxid is formed. I prefer to cut off thesupply of air during the final calcination in order to preventconversion of lead protoxid into a higher oxid at those parts of thefurnace that are insufficiently hot. Obviously this higher oxid wouldupon being further heated yield up again the oxygen by the absorption ofwhich it has been produced, and thus be reduced to protoxid; but thisreduction requires the action of a higher temperature and a large periodof time, which will be wholly avoided.

by conduct-ing the final calcination in the absence of air.

For carrying out the improved process the precipitate may be compressedin a partlydried state into solid blocks (in the shape of bricks,lengths of cylinders, the.) before burning. In consequence of theexpulsion of wa ter and carbonic acid these blocks will becomesufficiently porous to be capable of be ing burned throughout in thepresence of air without falling to pieces.

Where the burning operation has not been properly conducted and greateror less quantities of a higher lead oxid have formed, the same areunavailable in the formation of lead saccharate. They need not on thisaccount, however, be separated from the protoxid, but may be allowed topass through the saccharate-formin g and earbonatin g stage,and when theburning of the precipitate obtained in the latter stage is thenconducted in the proper manner they will be reduced to protoxid, givingup their surplus of oxygen, even at a moderate temperature, to theorganic substance present, so that in this case proportional less air orno air at all need be admitted.

The alumina, the silieic acid, and the oxid (sesquioxid) of iron presentin the precipitate may be rendered innocuous by mixing the washedprecipitate with finely-divided magnesia or carbonate of magnesia (sayabout two, three, or more per cent. of MgO of the quantity of protoxidof lead) and drying the mixture previous to calcination. On calciningthe mixture the said impurities, which otherwise would have adestructive effect upon the walls of the furnace, become whollyconverted into harmless magnesium compounds. An action similar to thatof magnesia is exercised by baryta, strontia, and lime and theircarbonates.

\Vhat I claim, and desire to secure by Letters Patent of the UnitedStates, is-

1. The process for recovering lead protoxid fit for extracting sugarfrom molasses and other impure sugar solutions by burning theprecipitate obtained by the carbonation of lead saccharate and otherwaste products containin g lead carbonate and organic lead salts, whichconsists in carrying out the burning in two phases, that is to say, infirst gently heating the material in the presence of air up to atemperature below the melting-point of lead until the black color hasdisappeared,and then at once raising the temperature to a dark-red heat,substantially as and for the purpose specified.

2. The process for recovering lead protoxid fit for extracting sugarfrom molasses and other impure sugar solutions by burning theprecipitate obtained by the carbonation of lead saccharatc and otherwaste products containing lead carbonate and organic lead salts, whichconsists in mixing the said material with magnesia or its describedequivalent, gently heating the mixture in the presence of air up to atemperature below the meltingpoint of lead until the black color hasdisappeared, and then at once raising the temperature to a dark-redheat, substantially as and for the purpose specified.

3. The process for recovering lead protoxid fit for extracting sugarfrom molasses and other impure sugar solutions by burning theprecipitate obtained by the carbonation of lead saceharate and otherwaste products containin g lead carbonate and organic lead salts, whichconsists in carrying out the burning in two phases, that is to say,in-first gently heating the material in the presence of air up to atemperature below the melting-point of lead until the black color hasdisappeared,and then at once raising the temperature to a dark-red heatand shutting out the air, substantially as and for the purposespecified.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

ALFRED \VOHL.

lVitnesses:

HENRY HASPER, W. I'IAUPT.

